diff --git a/op-service/txmgr/cli.go b/op-service/txmgr/cli.go
index 98c07a1eabdf7926e2d3f1957b2539a7f1cdc31b..8a972e7a524aa1cd6fd6d7660f65da2b54279713 100644
--- a/op-service/txmgr/cli.go
+++ b/op-service/txmgr/cli.go
@@ -100,6 +100,9 @@ func (m CLIConfig) Check() error {
 	if m.L1RPCURL == "" {
 		return errors.New("must provide a L1 RPC url")
 	}
+	if m.NumConfirmations == 0 {
+		return errors.New("num confirmations must not be 0")
+	}
 	if err := m.SignerCLIConfig.Check(); err != nil {
 		return err
 	}